Conventional continuous mining machines usually employ some system for feeding liquid to the drilling tool for cooling. The liquid, usually water, may be transferred along the shaft of the mining machine to outlets that spray the water against the wall face being mined.
Heretofore, this arrangement has proven to place costly restraints on the manufacture, operation and repair of such a machine. Generally in order to make such a machine serviceable without significant leakage of the water sealing system:(1) higher quality machining and material preparation is required; (2) heavier parts are required to reduce deflection and bearing play; (3) less severe usage is required to minimize distortion; and more (4) more care is required in field servicing because of potential distortion.
A prior suggestion has been made by others to build in a separate bearing system in the seal area to isolate the seals from the action of the machine. In this instance, the water cooling system is separated from the bearing by a water and oil interface seal. An additional seal and associated wiper is provided in the bearing and an additional water seal and associated wiper is provided adjacent the water transfer channel. The oil is fed to the water system bearing by conventional pressurized oil systems.
The drawbacks to this suggested system are also evident. First, the system is costly since two separate liquid feeding circuits are required and seals for both systems are necessary. The risk of contamination of the oil circuit with water from the water circuit is always present, and when it occasionally happens a costly shutdown of the mining machine is required.